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Offline juner

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How to Subnet, an Example
« on: December 07, 2013, 06:13:48 AM »
How to subnet the following IP:
10.96.42.37 /28


1) Determine your subnet mask based on the “slash” or “CIDR” notation (the /28).  It is about which bit is on and off in each octet, which I can explain more if anyone wants.  A quick reference to all relevant IPv4 subnet masks:

/1 - 128.0.0.0
/2 - 192.0.0.0
/3 - 224.0.0.0
/4 - 240.0.0.0
/5 - 248.0.0.0
/6 - 252.0.0.0
/7 - 254.0.0.0
/8 - 255.0.0.0
/9 - 255.128.0.0
/10 - 255.192.0.0
/11 - 255.224.0.0
/12 - 255.240.0.0
/13 - 255.248.0.0
/14 - 255.252.0.0
/15 - 255.254.0.0
/16 - 255.255.0.0
/17 - 255.255.128.0
/18 - 255.255.192.0
/19 - 255.255.224.0
/20 - 255.255.240.0
/21 - 255.255.248.0
/22 - 255.255.252.0
/23 - 255.255.254.0
/24 - 255.255.255.0
/25 - 255.255.255.128
/26 - 255.255.255.192
/27 - 255.255.255.224
/28 - 255.255.255.240
/29 - 255.255.255.248
/30 - 255.255.255.252

So the subnet mask of /28 is 255.255.255.240


2) Determine block size.  Simple, 256 - (the value of the octet you are subnetting in)

   In this case, “256 - 240” which is 16


3) Determine the network address of the subnet.  This is the first IP in the subnet, but it is not useable.  Start at 0, then count by the block size until you reach the range of the octet you are subnetting in.  In this case /28 is in the last octet, so based on IP 10.96.42.37 you are trying to find the range where .37 falls.  0, 16, 32, 48…  .37 falls in between 32 and 48, so 32 is the network address, more specifically 10.96.42.32 is the network address.


4) Determine the broadcast address of the subnet.  This is always the IP before the next network address.  Since, in step 3 we determined 10.96.42.32 is a network address, and 10.96.42.48 is the next network, 10.96.42.47 is the broadcast address.  The broadcast address is also not a useable IP.


5) Determine the number of useable host IPs.  Easy step…  (2^n)-2 where n = 32 - (the CIDR number).  In this case, 2^(32-28)-2=14.  It makes sense, the block size is 16, so there are 16 IPs in the subnet, you can’t use the network address or the broadcast address, so subtract 2.


6) Determine the useable host range.  Steps 3 and 4 are great, but you can’t use the IP addresses.  So, find out what you can use.  This is easy, the range starts at the IP after the network address, and ends at the IP before the broadcast address.  So, in this instance, the useable range is 10.96.42.33-10.96.42.47.



I have no idea why I posted this, but if you have any questions, or want to know more about networking in general please ask.


DISCLAIMER:  I AM NOT QUALIFIED
« Last Edit: December 07, 2013, 04:06:19 PM by junker »

Saddam Hussein

Re: How to Subnet, an Example
« Reply #1 on: December 07, 2013, 06:16:05 AM »
How do I use YouTube to hack a website?

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Offline juner

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Re: How to Subnet, an Example
« Reply #2 on: December 07, 2013, 06:17:05 AM »
How do I use YouTube to hack a website?

THAT IS OUTSIDE OF THE SCOPE OF THIS THREAD

I AM NOT QUALIFIED

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Offline jroa

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Re: How to Subnet, an Example
« Reply #3 on: December 07, 2013, 06:22:21 AM »
junker, good job.  My only suggestion would be to actually explain the purpose of a subnetwork, what the subnet mask does as far as dividing a network up, and a little better explanation on how the subnets interact with the networks. 

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Offline juner

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Re: How to Subnet, an Example
« Reply #4 on: December 07, 2013, 06:32:41 AM »
junker, good job.  My only suggestion would be to actually explain the purpose of a subnetwork, what the subnet mask does as far as dividing a network up, and a little better explanation on how the subnets interact with the networks.

Oh, fuck that.  If people have questions, they can ask and I will answer.

You subnet to get IPs.  I can also teach you all about the OSI, especially layers 2 and 3.  I am a pro, almost qualified.

Offline bj1234

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Re: How to Subnet, an Example
« Reply #5 on: December 07, 2013, 06:35:56 AM »
How does subnetting let me hack youtube videos?

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Offline xasop

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Re: How to Subnet, an Example
« Reply #6 on: December 07, 2013, 06:48:03 AM »
You subnet to get IPs.  I can also teach you all about the OSI, especially layers 2 and 3.  I am a pro, almost qualified.

Can you teach me about layer 6? It's the one I know least about.
when you try to mock anyone while also running the flat earth society. Lol

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Offline juner

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Re: How to Subnet, an Example
« Reply #7 on: December 07, 2013, 06:49:54 AM »
You subnet to get IPs.  I can also teach you all about the OSI, especially layers 2 and 3.  I am a pro, almost qualified.

Can you teach me about layer 6? It's the one I know least about.

lol no one uses presenation layer willingly

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Offline xasop

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Re: How to Subnet, an Example
« Reply #8 on: December 07, 2013, 06:59:31 AM »
lol no one uses presenation layer willingly

How would you know? You're not qualified.
when you try to mock anyone while also running the flat earth society. Lol

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Offline juner

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Re: How to Subnet, an Example
« Reply #9 on: December 07, 2013, 07:01:33 AM »
lol no one uses presenation layer willingly

How would you know? You're not qualified.

I know :(

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Offline jroa

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Re: How to Subnet, an Example
« Reply #10 on: December 07, 2013, 07:20:15 AM »
Can I subsnets with IVP6? ???

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Offline juner

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Re: How to Subnet, an Example
« Reply #11 on: December 07, 2013, 07:27:45 AM »

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Offline jroa

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Re: How to Subnet, an Example
« Reply #12 on: December 07, 2013, 07:45:12 AM »
Please explain. 

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Online Lord Dave

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Re: How to Subnet, an Example
« Reply #13 on: December 07, 2013, 02:07:44 PM »
I used to know this stuff but its been years.  Thanks for the refresher.
If you are going to DebOOonK an expert then you have to at least provide a source with credentials of equal or greater relevance. Even then, it merely shows that some experts disagree with each other.

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Offline juner

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Re: How to Subnet, an Example
« Reply #14 on: December 07, 2013, 04:02:56 PM »
Please explain.

https://supportforums.cisco.com/docs/DOC-17232

Cisco does it better.

This thread is based on IPv4 which I am nearly qualified in.  Keep questions related to that.  I can only hope to be qualified on IPv6 in the coming decades.

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Offline Rushy

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Re: How to Subnet, an Example
« Reply #15 on: December 07, 2013, 11:28:30 PM »
How do I brute force AES-256?

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Offline juner

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Re: How to Subnet, an Example
« Reply #16 on: December 07, 2013, 11:32:08 PM »
How do I brute force AES-256?

A lot of super computers, and a lot of time.

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Offline Rushy

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Re: How to Subnet, an Example
« Reply #17 on: December 07, 2013, 11:36:21 PM »
A lot of super computers, and a lot of time.

Well, you're not wrong.

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Offline juner

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Re: How to Subnet, an Example
« Reply #18 on: December 07, 2013, 11:42:20 PM »
A lot of super computers, and a lot of time.

Well, you're not wrong.

I am also not qualified.

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Offline Fortuna

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Re: How to Subnet, an Example
« Reply #19 on: August 10, 2021, 07:33:07 AM »
The worst thing about this shit is that everyone explains it a little bit differently. It's not even that difficult but there are 1000 explanations for it. I'm taking the Network+ next week and I'm just going to memorize the number of hosts and subnets for the /25 - /31 networks. Well, Get fucked CompTIA, if I have to do this IRL I'll just use a subnet calculator lmfao. What is this, 2001?

Also I tried to do your example in my head without looking at the answer and got to 16 subnets with 14 hosts in each, but class Cs are ez. If they ask me abnoout class A or B networks I'll just turn my computer off.
« Last Edit: August 10, 2021, 08:00:31 AM by Fortuna »